# Help please,

**URL:** <https://community.cartalk.com/t/help-please/5437>\
**Category:** Maintenance/Repairs\
**Created:** [October 3, 2007, 6:29pm UTC](https://community.cartalk.com/t/help-please/5437 "2007-10-03T18:29:01Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![TJScott2012](https://avatars.discourse-cdn.com/v4/letter/t/e68b1a/32.png) [@TJScott2012](https://community.cartalk.com/u/TJScott2012)\
**Post date:** [October 3, 2007, 6:29pm UTC](https://community.cartalk.com/t/help-please/5437/1 "2007-10-03T18:29:01Z")

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car jumps from 2000rpms all the way down and goes back up all the time and bogs while it does it

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**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\
**Post date:** [October 3, 2007, 6:33pm UTC](https://community.cartalk.com/t/help-please/5437/2 "2007-10-03T18:33:15Z")

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Could be a disconnected or leaking vacuum hose or a bad Idle Air Control (IAC) valve.

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**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\
**Post date:** [October 4, 2007, 12:26am UTC](https://community.cartalk.com/t/help-please/5437/3 "2007-10-04T00:26:24Z")

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Is the engine actually changing speed or is the tach showing a change and the engine not really changing?

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**Author:** ![TJScott2012](https://avatars.discourse-cdn.com/v4/letter/t/e68b1a/32.png) [@TJScott2012](https://community.cartalk.com/u/TJScott2012)\
**Post date:** [October 4, 2007, 1:35am UTC](https://community.cartalk.com/t/help-please/5437/4 "2007-10-04T01:35:19Z")

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the engine is changing right along with the tach, my teacher asked me and all i could think of was a vacuum leak, so i just posted here

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**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [October 5, 2007, 2:34am UTC](https://community.cartalk.com/t/help-please/5437/5 "2007-10-05T02:34:03Z")

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Use your Haynes repair manual to find the idle air control valve (iac). Disconnect the electrical connector from the iac. If the idle stabilizes, you’ve found your culprit. Another possibility is the mass air flow sensor (MAF). Follow same procedure.